In the manufacture of plastic play balls which are formed of stretchable plastic material, plastic balls of a predetermined size are received generally in heated condition from for instance an oven. The valve housing of each ball is then impaled upon an inflating needle and inflating fluid, such as air, is inserted into the ball to expand the ball to a predetermined finished size, with the heated stretchable wall material of the ball thinning out as the ball expands. A closure plug is then inserted into the valve opening in the ball after withdrawal of the inflating needle to permanently seal the inflating fluid interiorly of the ball, after which the ball is transported to another location for further handling. Many of these operations are manual and the result is increased costs for producing plastic play balls.